A wheel support bearing device for supporting a drive wheel is fastened to a joint outer ring of a constant velocity joint by means of a nut, and transmits a driving force to the drive wheel. The joint outer ring of the constant velocity joint abuts against a bearing inner ring. Therefore, there is a case that a bending moment applied to the bearing device and the constant velocity joint during a turn of a motor vehicle causes an abrasion due to a fretting or a creep of the bearing inner ring at an end face of the bearing inner ring and an end face or a back face of the joint outer ring, which is in abutment with the end face of the bearing inner ring. If such abutting end face of the joint outer ring is worn, an axial tension generated by fastening of the nut is lowered, and as a result, a slack of the nut, an abrasion of a fitting serration portion or the like may then take place. Further, an operating angle of the joint is changed in accordance with a steering of the wheel, and a great load is applied to a joint cup portion by a large steering. Such great load may cause a fatigue breaking or a static breaking in the joint.
Conventionally, in order to solve the above problem, there have been tried an increase of a thickness or a diameter, a usage of a high strength material, an addition of a thermal refining after forging, and the like. Further, a induction heat treatment has been utilized as a countermeasure against a bending fatigue of a stem portion and an abrasion of the end face of the bearing inner ring.
However, the increase of the thickness or the diameter causes an increase of a weight. Further, the usage of the high strength material causes a reduction of a workability and an increase of manufacturing cost. The addition of the thermal refining causes a further increase of manufacturing cost. Also, since a corner portion is formed between the abutting face of the joint outer ring and the cup, the induction heat treatment to the abutting face may cause overheating of the corner portion. Accordingly, there is a case that the abutting face can not be subject to a sufficient heating temperature and as a result, a quenching hardness is lowered. Further, such overheating of the corner portion may cause a quenching crack.